Removal efficiency of methylene blue (MEB) from aqueous media was studied under different experimental conditions of pH, contact time and initial concentration of the adsorbate. Activated rice husk biochar (ARHB) was characterized using BET surface area and XRD. The XRD diffraction indicated amorphous nature of the biochar with pore size (cc/g) and pore surface area (m2/g) of 9.369 and 27.32 respectively from BET surface area plot. Equilibrium isotherm based on coefficient of non-determination indicated the following order as best fit model: Hill ˃ Kiselev ˃Elovic ˃Flory-Huggins > Langmuir > Jovanovic > Harkin-Jura >Freundlich > Henry > Temkin >Redlich Peterson>Durbinin-Kaganer Redushkevich >Hill-de Boer > Fowler-Guggenheim. Based on the highest correlation coefficient and the lowest values of the error functions applied to the kinetic models, Weber and Morris intra-particle diffusion and liquid film diffusion were noted to be in control of the sorption rate. The MEB sorption capacity of the activated biochar was 356.99 mmolkg-1 which was in the range of commercially available activated carbons and other biosorbents.

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Copper(II) complexes of bis(4-hydroxypent-2-ylidene)diaminoethane (BHPDE) were prepared by extractive method. Job’s continuous variation and equilibrium constant methods, as well as spectral and elemental analyses were applied in the determination of the nature of extracted species. The results indicate the formation of mixed ionic complexes of the types Cu(H2L)X2, Cu(H2L)2X2and CuL (where H2L = BHPDE and X = NO3-, CIO4-, Cl-or ½SO42-). Cu(H2L)X2and Cu(H2L)2X2predominate at low pH extractions while CuL chelate predominates at high pH extraction. The complexes exist in two isomeric forms, the blue readily-water-soluble and the violet less water-soluble forms. Both complexes show maximum absorption at 540 nm and molar absorptivity values of about 2.0 x 102dm3mole-1cm-1.

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Composite soil samples were collected about 200 m 2 apart at 0-30 cm (top soil) and 60-90 cm (subsoil) depths from Enyigba Pb-Zn Mine and Abakaliki Urban during the dry season in December, 2010. The soils were analyzed for pH and total contents of As, Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn using Proton Induced X-Ray Emission (PIXE) Technique. Results show that total mean concentrations of the heavy metals decreased with depth. Whereas the mean concentrations of the metals in the top and sub soil of Enyigba Mine decreased respectively in the order, Fe > Pb > Zn > Cu > Mn > Cd > Co > Ni > As and Fe > Zn > Cu > Mn > Pb > Co/Ni > Cd > As in the subsoil, the top and subsoil of Abakaliki Urban showed similar trend in the order, Fe > Mn > Pb> Zn > Co/Cu > Ni > Cd > As. The total mean concentrations of the metals in the top and sub soils of Enyigba Mine were found to be higher than those of Abakaliki Urban. Elevated concentrations of Pb > Ni > Cd above the US-EPA Regulatory Limits in that order was observed only in the Enyigba Mine top soil, while variations in the heavy metal levels were generally observed between and within groups. The mean soil pH obtained in Enyigba Mine and Abakaliki Urban was 6.5 and 6.8 respectively.

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